Heavy usage hot water

[Laith J]

Good evening all,

 

Just wondering if there are any people on here who are knowledgeable with plumbing..

 

I am currently working on a conversion of a property in to a 9 bedroom HMO with separate bathroom for each room and small kitchenette area.. This will mean I need 9 showers, 18 sinks (one in each kitchen area one in each bathroom, 9 toilets, and 2 washing machines. At present there is only a single 20mm cold water supply to the property..  It may also be useful to point out that I will need a radiator in each bedroom and a towel rail in each bathroom, along with a radiator in each of the three hallways. If anyone could help answer or direct me regarding the following questions I would be very grateful

 

* How many 300l cylinders can be heated from a high KW system boiler? is it just the one? (Thought here is to have x number of cylinders in the attic space and rely on gravity)

* (roughly) How many electric showers could be run off the existing supply (assuming electricity supply is not an issue and assuming all showers are on at the same time)?

*How many and what size old water supply/upgrade would be recommended? 

 

Thanks in advance

 

[ProDave]

What electricity supply at the moment?

 

At a push you can run 2 showers from a 100A single phase supply, or 6 from a 100A 3 phase supply.  So electric is not the way if you want 9 showers.

[Laith J]

3 minutes ago, ProDave said:

What electricity supply at the moment?

 

At a push you can run 2 showers from a 100A single phase supply, or 6 from a 100A 3 phase supply.  So electric is not the way if you want 9 showers.

Im awaiting the electricity board to confirm the current supply

[Simplysimon]

what are you converting from, a standard large domestic property?

[Laith J]

It was previously a 7 bed HMO but I wasn't involved up until now so i have very little knowledge of what was there as it is now a shell (following strip out)

[SteamyTea]

Re the space heating. Have you considered air2air for each room.

With a bit of careful ductwork you can fit it in with the ventilation system.

You can basically heat as many cylinders as you like as long as the heat source is large enough.

By using cylinders you can heat them overnight at a cheaper rate.

There is also Sunamps. One for each room, if there is the space.

[Laith J]

14 minutes ago, SteamyTea said:

Re the space heating. Have you considered air2air for each room.

With a bit of careful ductwork you can fit it in with the ventilation system.

You can basically heat as many cylinders as you like as long as the heat source is large enough.

By using cylinders you can heat them overnight at a cheaper rate.

There is also Sunamps. One for each room, if there is the space.

The heat source would be gas... I suppose what matters is the reheat time of the cylinders if most of the showers were being used at the same time

 

I haven't heard of air2air but i'll look in to it, thanks

 

[SteamyTea]

29 minutes ago, Laith J said:

I suppose what matters is the reheat time of the cylinders if most of the showers were being used at the same time

If each shower is using 10 kW of energy, and you have a store of 200 kWh, then with no reheating, you get 20 minutes of shower time if they are all running.

To reheat that lot with a 50 kW heater would take 4 hours.

The usual demand on for bathing is considered 3 kWh/day.

[Nickfromwales]

Segregate potable ( drinking quality ) water system and bathing water systems from the get go and then go for a pressurised artificial cold mains created by 3x 500L cold mains accumulator vessels. 
Hot water cylinders or Sunamps can provide all the hot water you’ll need, and you want to aim for around 600L of stored hot water. That would be 2x 300L UVC’s or 3x size 9 Sunamps. UVC’s need annual G3 inspection but Sunamps do not. Cost is roughly x2 to go for Sunamps but the form factor is also beneficial as it’s a factor of about 3 compared to UVC’s ( Sunamps being smaller / compact / less complex ) so less space needed for the same capacity.

Its down to how much space you have? What plant space is available?

You can also go for gas instants, one per floor, for instant hot water, with something like a Rennai 50kW instant gas multipoint. 
Cold mains will be the killer here as no cold in = no hot water out, regardless of what provides hot water  

Whos paying the gas / electric bills? 

[Laith J]

On 22/01/2020 at 21:40, Nickfromwales said:

Segregate potable ( drinking quality ) water system and bathing water systems from the get go and then go for a pressurised artificial cold mains created by 3x 500L cold mains accumulator vessels. 
Hot water cylinders or Sunamps can provide all the hot water you’ll need, and you want to aim for around 600L of stored hot water. That would be 2x 300L UVC’s or 3x size 9 Sunamps. UVC’s need annual G3 inspection but Sunamps do not. Cost is roughly x2 to go for Sunamps but the form factor is also beneficial as it’s a factor of about 3 compared to UVC’s ( Sunamps being smaller / compact / less complex ) so less space needed for the same capacity.

Its down to how much space you have? What plant space is available?

You can also go for gas instants, one per floor, for instant hot water, with something like a Rennai 50kW instant gas multipoint. 
Cold mains will be the killer here as no cold in = no hot water out, regardless of what provides hot water  

Whos paying the gas / electric bills? 

At present it hasnt been decided who will pay the bills, but the likelyhood is that bills will be inclusive with rent. 

 

If needed we can play around with layouts to fit any of the different options you have suggested. There is potential to create a loft space which could be used to home 2x 300l cylinders and I was thinking of possibly using a gravity fed system - would this mean I wouldn't need to upgrade the incoming cold mains?

[PeterW]

Gravity won't work here - you will get appalling pressure and tbh you need to ensure the cold cisterns don't go dry which is a distinct possibility in this situation.

 

Why does the owner/landlord want to skimp on conversion costs..?

[Laith J]

Also nick, do sunamps need solar panels?

[Laith J]

18 minutes ago, PeterW said:

Gravity won't work here - you will get appalling pressure and tbh you need to ensure the cold cisterns don't go dry which is a distinct possibility in this situation.

 

Why does the owner/landlord want to skimp on conversion costs..?

Apologies if I have implied in any way that the owner is skimping on costs, as yet he has had no input and it is more a case of me trying to find a workable solution with associated costs for each option. The gravity fed system was my idea but admittedly I am no expert in heating and water systems. My thought process was that if pressure was poor from gravity then possibly the addition of a pump would help

[PeterW]

To do it properly it is going to cost - a lot. 
 

Holding upward of 1,000 litres of hot water, preferably at mains pressure, won’t be cheap and because these are individual units you will need to deliver as though it’s all in parallel. When you have 9 rooms and 4 showers you can limit the usage but in this case you need to potentially diversify. 
 

Electric showers aren’t ideal, but depending on the building layout you could have attic cold tanks serving the ground floor electric showers. Then the next floor would be mains pressure using either UVC or potentially Sunamp (as per @Nickfromwales this may help as they are small) and this would need good water pressure but it would mean if a flat “ran out” then it would be isolated to that unit. 
 

Have you got any floor plans ..?? 

[Nickfromwales]

17 hours ago, Laith J said:

Also nick, do sunamps need solar panels?

No. Any external heat source capable of generating 62oC or above is fine. Plus you can opt for an ‘e’ prefix unit which then features a 3kW immersion heater for back up.

‘Duals‘ have 2x heat exchangers in each SA unit. One for potable DHW, and the other to be dedicated to importing heat to recharge the SA. The immersion will be nigh on useless for your situation, if you’re thinking electric only, but if burning gas then you’d be fine.

You do not want to fit accumulators in the attic, only CWS ( cold water storage ) tanks ( open / gravity ). 
I’ve done an HMO with 14 en-suites for which we just used a few big CWS tanks, gravity hot water to basins / sinks / baths, and took feeds out of the same CWS’s to tank fed electric showers ( Triton T80Si pumped ) which worked brilliantly. Needs 3 phase electric to run that lot though Sonos a big wiring job / upgrade. Also you will need to run separate potable water supplies from the cold mains to sinks / basins / kitchen & utility, as the stored water CWS based system can only be for bathing as it will be unfit for human consumption. 

You could take a feed from attic CWS to a pump and pair of 500L accumulators on the ground floor and get a sealed and pressurised system working ( so you could use thermostatic mixer showers ), which would still need potable segregation, but better still would be an outbuilding where you could fit 3 or 4 x 500L ACC’s and just go mains pressurised with no pumps / CWS / tank fed showers etc. Uber low maintenance option too. Just hook up a gas boiler to 3x size 12 SA’s and you’re rocking and rolling. If you have room for UVC’s then they’d work too, but would take up probably 2-3 times the space the SA’s would need, plus you’ll need G3 annual service / inspection on top of the gas cert. Over 10 years the SA’s would break even in cost, but you COULD, possibly, get away with a single 500L UVC just would be down to usage patterns and estimating peak demand eg if students then lots of evening showers at the same time etc. 
It’s a big system that’ll need a proper design, rather than back of a fag packet, so measure twice cut once ?